The objective of this research is to understand the course of membrane differentiation in human myeloid (granulocyte-monocyte) cells and to compare membrane differentiation of normal cells with that of leukemic cells by using surface glycoproteins as onco-differentiation markers. Two major aspects deal with: (1)\Characterization of membrane glycoproteins expressed on leukemic cells and normal cells at various stages of differentiation and maturation. We have found that distinctly different sets of cell surface glycoproteins are expressed in leukemic cell lines representing early and late stages of myeloid cell maturation. Studies are in progress to isolate and characterize such glycoproteins (gp130). Further aims will be to prepare antibodies specific to such glycoproteins and analyze membrane differentiation in normal and leukemic conditions. In addition, changes of cell surface glycoproteins during in vitro differentiation of HL-60 and ML cells will be analyzed. (2)\Characterization of the changes in the carbohydrate structures of cell surface glycoproteins during the process of differentiation of normal and leukemic cells with special reference to lactosaminoglycan. We have found by using the newly developed technique of cell surface labeling and endo-beta-galactosidase digestion, that lactosaminoglycan displays a drastic change during myeloid cell maturation. In addition, preliminary studies suggest that less mature cells are more sialylated in cell surface glycoproteins. Structural studies will be performed on carbohydrate chains of cell surface glycoproteins (gp105, gp95, gp130) of various myeloid leukemic cell lines representing different stages of maturation.